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The new ideas will strengthen the controversial connection between mass extinctions and impacts. Currently there is only one know impact crater that coincides with a mass extinction. The Chicxulub Crater, North Mexico, is believed to have helped exterminate the dinosaurs 65 million years ago.
This new research published in the Science journal ties in a known mass extinction event with an asteroid impact. The event happened 380 million years ago in a time period called the Devonian. It was a time when only small plants, wingless insects and spiders inhabited the land, the majority of life dominating the sea. The fossil record shows 40 per cent of species disappeared at this time.
The Earth�s 4.5 billion year history is divided in to several groups to form a geological time scale. The past 550 million years divide into 90 groups with each stage distinguished from another by a change in the fossil record, like that found at the Cetaceous-Tertiary Boundary (K-T), the mass extinction at the time of the Chicxulub Impact.
The evidence for the new theory comes from rock layers in Morocco laid down about 380 million years ago. Debris within the sediments looks to have come from a from a cataclysmic explosion. The layer has unusual magnetic properties and contains grains of quartz that seems to have experienced extreme stress, a feature common to impacts.
Although the signs indicate a catastrophe that coincides with a disappearance of animals. Other researchers have agreed that there was an impact around the time, but feel the evidence for a related mass extinction is weak. If is impact proves to correlate with the Devonian extinction it would be the second impact-extinction event and with several extinctions not linked to celestial collisions it will fire the ongoing debate.
More info: Louisiana State University
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